As the main focus of the article is not the theoretical construction of FR curvature, we will just provide an overview of it, referring the reader to Forman's original article [1]} for a more detailed and formal discussion. FR curvature was originally designed for weighted CW-complexes, which is a big class of topological objects that contains undirected weighted networks (for an introduction to CW-complexes and other algebraic topology concepts, we refer the reader to the classical book by Hatcher [2]}). The original, general formula for FR curvature (see Theorem 2.2 in [1]}) requires defining and keeping track of an orientation on the whole CW-complex, which could slow computations down. Fortunately, networks without multiedges are a special type of weighted CW-complex named “quasiconvex” (see Definition 0.1 in [1]}), which essentially means that the intersection of two \(n\) -dimensional objects of the complex is at most one \((n-1)\) -dimensional object (for networks, any two edges must share at most one vertex – that is, no multiedges). For quasiconvex complexes, the FR curvature formula can be simplified to one that no longer needs an orientation (see Theorem 3.10 in [1]}). Using this, one gets that the Forman-Ricci curvature of a network edge \(e=(v_1,v_2)\)  is [6]}
